Filip and Albin, both aged ten, were digging in the school sandpit one breaktime when their spades reached the ground underneath the box. That was where they found a curious-looking coin, which they showed to their teachers at Yngsjö Skola in Kristianstad, Skåne.
"It's a copper coin, a little bit green because that's what happens to copper, and we think that it's one sixth of an öre, so a very small amount – I don't think that a lower value has been printed!" Mikael Ringman, press officer at Skåne's County Administrative Board, told The Local.
"On the top it has three crowns, and it's from the reign of Karl XI."
"The boys were digging, which apparently a lot of the kids at the school enjoy doing, when they happened to see this coin. They thought it was modern and asked to keep it, but the teachers saw that it seemed pretty old," Ringman explained.
In Sweden, any discoveries made by members of the public of items believed to be more than 150 years old must be reported to the local county administrative board, and that's what the teachers did, sending a letter signed by the school's third and fourth graders along with photos of the coin.
It was then up to the county board to contact the Swedish National Heritage Board, which confirmed this week that the coin, while unusual, was not rare enough for the state to need to buy it.
This means the coin will be kept by the school, which will display the artefact along with objects from the school's history.
Ringman said the county board in Skåne typically deals with two or three inquiries about archaeological finds, including coins, each year.
But the discovery of the coin doesn't quite top the archaeological find made by Swedish-American eight-year-old Saga, who unearthed a pre-Viking era sword in a lake earlier this year.
That discovery earned the girl the title of 'Queen Saga' on social media and sparked international interest. However, unlike the boys in Yngsjö, Saga's discovery was too valuable for her to keep it.
READ ALSO: The Local's interview with sword-finder Saga